The present invention relates to a method for making a bulked web. Bulked materials, such as bulked nonwoven webs are particularly well suited for use in disposable absorbent articles such as diapers, incontinence briefs, training pants, feminine hygiene garments, and the like, as they are able to handle fluid in a manner which improves the articles performance.
Nonwoven webs may be manufactured into products and components of products so inexpensively that the product may be viewed as disposable after only one or a few uses. Representatives of such products include diapers, training pants, wipes, garments incontinence briefs, feminine hygiene garments and the like.
Nonwoven webs may be treated to provide the nonwoven web with certain properties. For example, U.S. Pat. No. 5,244,482 issued to Hassenboehler, Jr. et al. on Sep. 14, 1993 discloses a method for treating a nonwoven web wherein the nonwoven web is heated at an elevated temperature and uniaxially drawn to consolidate and stabilize the nonwoven web. Such nonwoven webs are noted to exhibit an increased elasticity after processing. Such elasticity increase is recognized as being caused by the new xe2x80x9cmemoryxe2x80x9d instilled by the heating of the nonwoven web. For applications desiring enhanced extensibility rather than elasticity, such heating is therefore not desirable. Additionally, such drawing and setting of the nonwoven web by heating at an elevated temperature often causes fiber embrittlement and the nonwoven web to exhibit increased gloss. For many applications involving skin contact, e.g., such as in diaper coverstock, such attributes are contrary to the desired cloth-like properties of softness and non-plastic, (low gloss) appearance. Lastly, the requirement of heating the nonwoven web to consolidate and stabilize the web adds to the complexity and cost of the process.
U.S. Pat. No. 4,981,747 issued to Morman on Jan. 1, 1991, discloses a xe2x80x9creversibly neckedxe2x80x9d material. It is taught that the unstabilized necked material must be held under high tension on the re-wound roll until such time as the further heat setting step is performed to stabilize the material. Such a material will again suffer the deficits noted above with respect to preferred skin contact applications, and will enhance the elastic properties of the material rather than the extensible behavior of the material.
U.S. Pat. No. 5,226,992 issued to Morman on Jul. 13, 1993, discloses a method of producing a composite elastic necked-bonded material. A tensioning force is applied to at least one neckable material, such as a neckable nonwoven web, to neck or consolidate the material. Instead of heating the consolidated nonwoven web, this patent teaches superposing the tensioned consolidated nonwoven web on an elastic material and joining the tensioned consolidated nonwoven web to the elastic material while the tensioned consolidated nonwoven web is in a tensioned condition. By joining the tensioned consolidated nonwoven web to the elastic material while still in a tensioned condition, the nonwoven web is constrained to its"" necked dimension. Such a procedure does not provide a means for producing a stabilized extensible web without the attachment of the nonwoven web to an additional elastic layer.
It is also an object of the present invention to provide a post-processing method for producing a stabilized bulked web.
It is an object of the present invention to provide a stabilized bulked web, capable of being wound into stable rollstock or festooned form, suitable for subsequent conversion or combining operations.
As used herein, the term xe2x80x9cstabilizedxe2x80x9d refers to a material of the present invention which is capable of being stored in a stable condition in any common or conventional web storage manner. Such storage means would include for example, low tension rolls or festooned material in boxes.
As used herein, the term xe2x80x9cnonwoven webxe2x80x9d, refers to a web that has a structure of individual fibers or threads which are interlaid, but not in any regular repeating manner. Nonwoven webs have been, in the past, formed by a variety of processes such as, for example, meltblowing processes, spunbonding process, and bonded carded web processes.
As used herein, the term xe2x80x9cpolymerxe2x80x9d, generally includes, but is not limited to, homopolymers, copolymers, such as, for example, block, graft, random, and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term xe2x80x9cpolymerxe2x80x9d shall include all possible molecular geometric configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic and random symmetries.
As used herein, the term xe2x80x9csurface-pathlengthxe2x80x9d refers to a measurement along a topographic surface of the material in question in a specified direction.
In accordance with the present invention there is provided a method of producing a bulked web comprising the steps of:
providing a web;
feeding the web in a first direction;
subjecting the web to incremental stretching in a direction perpendicular to the first direction to provide a bulky web; and
stabilizing the bulky web to provide a stabilized bulked web.
The method may also comprise the additional step of gathering the bulky web after the web has been subjected to incremental stretching in a direction perpendicular to the first direction. The step of gathering the bulky web comprises feeding the web through a cross-directional web diverting device.
The method may also comprise the additional step of winding nonwoven web onto a take-up roll or festooning the nonwoven web into box.